Method of and means for testing



April 13, 1937. E. o. RHODES 2,076,592

METHOD OF AND MEANS FOR TESTING Filed 001;. 23, 1955 \2 WI 26 ii? lillllhlllw GNIW Patented Apr. 13, 1937 UNITED STATES METHOD OF AND MEANSFOR- TESTING Edmund o. Rhodes, Pittsburgh, Pa., assignor, by memo ents,to Koppers Company, a

corporation of Delaware Application October 23, 1935, Serial No. 46,364I Claim8.

This invention relates to improvements in methods of and apparatus fortesting the stability of plastic and semi plastic materials andmixtures. Stability testing apparatus have heretofore been employedwhich comprise an ordinary scale and means whereby a load is applied toa specimen to force the material of the specimen through an orifice. Onesuch apparatus includes a cylindrical mold having an orifice in thebottom thereof. A cylindrical plunger is provided and fits 5o ou ers 511193 1 Y snugly in the mold. The diameter of the plunger is therefore thesame as the inner diameter of the mold, but substantially greater thanthe diameter of the orifice. A cylindrical test specimen is 5 placed inthe mold and occupies the entire space between the bottom of the moldand the plunger so that one end of the specimen lies across the orificeand rests on an annular solid portion of the bottom and the entire areaof the other end of the specimen coincides with, and is acted upon by,the end-face of the plunger. The maximum resistance developed in forcingthe material of the specimen through the orifice is determined from thescale and is taken as a measure of stability of the material tested.

The stability of a plastic material has been defined as a measure of theresistance offered to the force causing flow immediately before failinby shearing and tension occurs. An'object of the 0 present invention isto provide an apparatus wherein improved means are employed to apply aload to a test specimen in a highly effective manner so as to representmore exactly a shear stress within a test specimen by the applied load.

Fig. 1 is a perspective viewof the complete apparatus employed in thetest; 7

t the a verawss ow 'm- 'i he apparatus'shown, in F The apparatus and themethod of the present is a vertical sectional viewof portion l c e m s mey ihav a idi s w g ts .l-yan aan e r e ror 4 on amend Pla atm ane es sate s a fl I ribe. minerals i IWhiQh .th'e s e men e. testedis placed. A"The mean -ir an mia-P 11 n (Cl. 265-11) I testing ring 9 is bevelledupwardly and presents as little frictional surface as possible. Aspecimen II to be tested, preferably premolded to fit in the mold 6, isshown in position for test and rests on the testingring 9. A removablespacing member i2 is placed within the mold 6 and its lower end rests ona surface of the specimen II. The member l2 receives a plunger i3 thelower end face of which, on commencing a test, is brought firmly againstthe surface of the specimen within the member l2.

An important feature of the present invention is the provision of aplunger i3 of smaller cross sectional area than that of the bottom ofthe mold 6 in which the plunger operates. The end face of the plungerbrought against the specimen is of an area substantially equal to butpreferably smaller than the area of the orifice in the bottom of themold 6. The axis of the plunger if extended, passes through the center.of the orifice Ill. The face of the plunger is applied to the testspecimen so that a core of the material of the specimen is forcedthrough the orifice I0. Regardless of the cross sectional shape of the.plunger or the shape of the orifice, these shapes geometrically speakingshould preferably correspond or be similar andthe distances betweenthecenter of the face of the plunger to the-outer edge of the said facecorresponding to the distances between the center of the orifice and theedge thereof should be substantially equal. The said distances may,however, be slightly less in the case of the face of the plunger ascompared with the corresponding distances in the case of the orifice.

The core of the material forced through the orifice in the mold shown inthe drawing is substantially the shapeof a frustr 'im of a cone when thearea of the face of the plunger is smaller than the area of the orifice.The core is substantially cylindrical in shape when the area of the,face of the plunger is equal to the area oflthe orifice. ,1' In anycase, the core forcedout by the plunger has a less cross se'ctional areathroughout its length than'the crosssectionalarea of the test specimeniii any plane: substantially at right angles to the. i lfition ofthemovementbfthejcora' v finga. test, tli fllungerjit is actuated byTa pung od 1 l that e t nd rania drivi em bh-f anism downwardly to.the'platfo'rm 4 ofthe scale. Th wmbldf fi h e etth man erj od 1 1 cents;Pi-th plu ge 1 so that the rounded 'end lls ofthe-rod llgages the ll 1nu s nro iii-simian n tan cim ns lB.m u iona e eve ed, we e meow I6 areve -whe l l8 and is by means of any suitable gear arrangement providedin a gear box 20. The bevel wheel I9 is mounted on a vertical spindle 2|provided on its upper portion with a continuous thread 22. 5 The spindle2| is prevented from any vertical movement by thrust bearings located ina clamp 23. The clamp 23 is rigidly attached to a vertical cylindricalsupport 24 which in turn is attached to the platform I1 by a clamp 25.10 The upper threaded portion 22 of the spindle 2| extends through athreaded passage in a sliding clamp 26 rigidly attached to a verticalcylindrical member 21 to which is connected the plunger rod ll. Theclamp 26 is providecLwith two arms 15 having bearings 28 and 29 thatslide along the cylindrical support 24. The rotation of the threadedmeans 22 causes vertical movement of the clamp 26 which in turntransfers vertical movement to the member 21. The movement of 20 themember 21 is guided by a bearing 3|! on the atively low velocity to theplunger rod M with a given speed of the motor "5. 25 In conducting atest on a binder for bituminous road material, a test sample is preparedfrom a mixture of about 9'? per cent by weight of standard Ottawa riversand and about three per cent-by weight of the binder. For testing suchmaterial, a 3 cylindrical mold having an inside diameter of as small asone inch and a height of one'and onehalf inches may be used. The testingring may in this instance have an opening seven-eighths of an inch indiameter. About fifteen grams of the 35 above mixture are placed in themold 6. The mold is then brought to a temperature of about 25C.whereupon the mixture is subjected to a pressure of approximately 3300pounds per square inch for about 1 minute. After this operation thespecimen of the above mixture fills the mold to approximately one-halfits height.

For proper comparison each sample of materials tested is subjected tothe same conditions before testing. If desired, a bath (not shown) hav-45 ing thermostatically controlled heating means may be provided for themold by which materials may be maintained at a uniform temperature whileunder test. Different materials may be tested under different conditionsdepending large- 50 1y on the conditions under which they are used.

The parts of the means are assembled. as shown in Fig. 2 and placed onthe platform 4 of the scale under the plunger rod H as set forth above.The sliding weights 2 and 3 are adjusted to balance the weight on theplatform. The motor [8 is started and the end of the plunger rod H incontact'with, .the plunger l3 moves the .latter down into the mold. Asatisfactory velocity at which the plunger rod I4 is moved is aboutthree 60 inches per minute.

With progressing motion of the plunger rod i4 the scale platform isdepressed and the pressure applied at any given moment to the testspecimen H is indicated by the scale. Immediately after 65 the yieldpoint of the test specimen has been cal member 24 above the balance beam33 of the scale. One 'end 36 of the lever 33 is. attached to the balancebeam 35 by means of a flexible chain 31. A counterweight 33 is hung on ahook 39 provided on the opposite end of the lever 33. To prevent undueinterference of the lever 33 with the plunger rod II, a slot 40 may beprovided in the lever through which the plunger rod passes. By thisarrangement the counterweight 33 applies an upward force tothe scaleplatform, thus opposing the presure transmitted to the platform by theplunger rod 14. By increasing the mass of the counterweight 38, themaximum capacity of a scale may be increased many times without undulyimpairing the accuracy of the scale.

The herein described test may be employed to determine the bindingproperties of any given plastic substance as well as the stability ofthe plastic itself. Any aggregate or filler of uniform size and shapemay be mixed with a binder, and

test specimens prepared therefrom.

By reason of the'arrangementof parts employed in the apparatus shown inthe drawing, it is possible to provide testing units that are ofrelatively sniall size particularly adapted to use in smallerlaboratories and to be placed on laboratory tables. Reliable results areobtained, and the force exerted upon -the plunger in the mold of thepresent apparatus, represents a truev shear stress within a testspecimen.

I claim:

1. In apparatus for testing the stability of plastic and semi-plasticmaterials and mixtures, I

the said apparatus including a mold adapted to receive a test specimen,the said moldbeing provided with an outlet orifice and a plungeroriiice, a plunger movable into the said mold and in alinement with thesaid outlet orifice, means for actuating the said plunger to load thetest specimen, and means for indicating the resistance developed inforcing a portion of the said test specimen through the said outletorifice; the surface area of the face of the said plunger in contactwith the surface of the test specimen being slightly less than tosubstantially the same as the area of the said outlet orifice but not asgreat as the area of the face of the specimen acted on by the saidplunger.

2. In a method of testing the stability of plastic and semi-plasticmaterials and mixtures, which method comprises preparing a test specimenof predetermined weight by compacting the material to be tested at apredetermined pressure and temperature and for a predetermined period oftime, the steps of confining the specimen of material, applying pressureto a portion of the surface of the specimen to force a core of the saidmaterial out of the said specimen and determining the pressure requiredfor forcing the said core through the material of the specimen, the saidcore throughout its length having a less cross sectional area than thecross sectional area of the specimen in any plane substantially at rightangles to the direction of movement of the said core.

'3. In a method of testing the stability of plastic and semi-plasticmaterials and mixtures, the steps comprising confining a specimen of amaterial, applying pressure to a portion of the surface of the'saidspecimen to force a core of the said material out of the specimen, anddetermining the pressure required for forcing the said core through thesubstance of the said specimen, the said core throughout its lengthhaving a less 5 plastic and semi-plastic materials and mixtures,

a chamber for material to be tested, the said chamber having on one sidethereof an outlet orifice and on an opposite side thereof a plungerorifice, and a plunger movable through the 10 said plunger orifice intothe said chamber and toward the said outlet orifice, the said plungerbeing in substantial alignment with the outlet orifice and having an endface substantially corresponding to the orifice in figuration but not 15exceeding the latter in area.

5. In apparatus for testing the stability of plastic and semi-plasticmaterials and mixtures, a chamber for material to be tested, the saidchamber having on one side thereof an outlet orifice and on an oppositeside thereof a plunger orifice, a plunger movable through the saidplunger orifice into the said chamber and in alignment with the saidoutlet orifice, and guide means for preventing the plunger from applyinga direct pressure on material in the portion of the chamber around thesaid plunger orifice and the said outlet orifice.

EDMUND O. RHODES.

